Specific heat and magnetization of the superconductors: osmium and the monoxides of niobium and titanium

The specific heat of a pure polycrystalline osmium sample (resistivity ratio 500) was measured between 0.18 and 4.20K in zero magnetic field. The transition from superconducting to normal state occurs at T0 = 0.638 +- 0.0020K. In the normal state, the coefficient of the electronic contribution is 2.050 +- 0.003 mJ/mole K2, and the Debye temperature at absolute zero, THETA0 = 467 +- 60K. In the superconducting state, the electronic specific heat is in agreement with the relation C/sub es/ = aγT0e/sup -bT0/T/ where a = 9.8 and b = 1.51. The critical field parameter H/sub c/(0) deduced from specific heat data is 77.5 gauss, and the maximum deviation of the critical field curve from the parabolic law is 4.3%. The value of the superconducting energy gap derived from γ, T0, and H/sub c/(0), is 3.55 k/sub B/T0 and the gap is found to be nearly isotropic. The specific heat of five NbO/sub x/ samples of different compositions (x = 0.96 to 1.02) was measured in the Meissner, mixed, and normal state. Niobium monoxide is found to be a weak coupling superconductor but the Meissner state parameters are in poor agreement with the BCS theory. NbO remains type II for all oxygen concentration. Magnetization data were taken for six different samples at two fixed temperatures. Specific heat results are given for seven titanium monoxide samples of compositions ranging from 0.91 to 1.17. The normal state results of all compositions are compared to previous theoretical and experimental work. From the coefficient of the electronic specific heat, the density of states at the Fermi surface are calculated for different compositions and compared to the band structure calculations. The superconducting state results of both TiO1.06 and TiO0.95 cannot be described by the BCS theory due to the broadness of the transition which might be a consequence of composition gradients within the sample